How many kinds of poplars are there?

Poplar is widely distributed in China, from Xinjiang to the eastern coast, from Heilongjiang and Inner Mongolia to the Yangtze River basin in the north. Poplar is the main afforestation tree species, whether it is shelter forest or timber forest. Especially in recent ten years, the area of poplar plantation in China has been expanding, and it has become the largest country in the world. The classification system of Populus is divided into five groups, namely, Populus (Leuce), Populus (Tacamahaca), Populus (Aigeiros), Populus (Turanga) and Populus (Leucoides). Yang Ya School of Mountain and Yang Ya School of Yapai Mountain in Bai Yang, P. tremuloides, P. adenopoda, a subgroup of Populus euphratica; Low temperature resistance (40 north latitude); The requirements for soil are not strict; Pure or mixed Betula platyphylla forest can be formed mainly by regeneration of sprouting strips (the survival rate of artificial propagation afforestation is very low). Populus alba has white reverse leaves and special-shaped leaves, which are distributed in countries around the Mediterranean, Central Europe, Eastern Europe, Central Asia and West Asia, and Xinjiang, China. Heat-resistant, high-temperature-resistant, wind-resistant and certain saline-alkali soil. Arid climate can be anywhere with water; Cutting propagation is easy. Populus Xinjiang is a variety of Populus alba. Populus tomentosa is the hybrid origin of Populus tomentosa (including Populus davidiana, Populus alba, Populus hopeiensis, Populus Xinjiang, etc.) distributed in Central Europe and West Asia. ), and the reproductive organs are not well developed; Unique to China; The content of poplar species in different producing areas is different, forming different provenances. Tree species with long life, good material, good dry shape, rapid growth in the early stage, difficulty in asexual reproduction, low survival rate of afforestation and strong preference for light intensity are affected. Suitable for being around, not cold-resistant, and parts of Liaoning are frozen. (2) There are two important species of Populus cathayensis abroad, that is, in North America: Populus tomentosa and Populus ainsliaea in western North America. The Great Lakes region of North America is the region with the largest variety of Populus davidiana in China. The latitudes from north to south are: Caragana wusuli, Caragana sauvignon, Caragana koreana, Caragana Huaxia, Caragana simonii and Caragana Sichuan. A) Populus yunnanensis is a moderately humid poplar with strict requirements on ecological conditions and site conditions such as soil humidity and atmospheric humidity, and it is easy to be infected with canker. The utilization value is second only to poplar and poplar. (3) Populus americana is an important tree species. There are only two varieties, Populus americana and Populus europaea. In China, only the Altai region of Xinjiang has the distribution of Populus deltoides. Populus deltoides and Populus deltoides (p.del. var。 Nostoc commune), Populus Missouri (p.del. var。 Missouri) and Angula Tower (P.del. var。 Angulata) Remarks: China Populus× Populus× Populus× Populus× Populus× Populus× Populus× Populus× Populus× Populus× Populus× Populus× Populus× Populus× Populus× Populus× Populus× Populus× Populus× Populus× Populus× Populus× Populus×) Yucheng, Henan, 2000. North America is distributed along the Mississippi River, and the positive species of plain and alluvial soil are not naturally distributed in China. They are all fast-growing timber forest species introduced in the early stage, and they are also the parents of Populus euramericana. There are three varieties from south to north, the subspecies are as follows: branchlets from edge to circle, leaves from big to small and fast, slow growth, variation, early leaves, difficult rooting in the later stage, easy to resist variation and strong disease resistance, and weak. The introduced tree species in China are: 63 poplar, 69 poplar, Shanhaiguan poplar, 50 poplar and 36 poplar. All were introduced from clones of Populus deltoides. Populus americana× Populus euramericana, as the most important way to improve Populus euramericana, uses its target heterosis to cultivate early-maturing Populus euramericana clones with good dry type, strong asexual reproduction ability and strong relative stress resistance. The successful clones were Populus canadensis, Populus Jian, Populus I-2 14, Populus alba and Populus 72. (4) There is only one species of Populus euphratica, mainly distributed in Central Asia and West Asia (Mediterranean countries; But Kenya likes light and heat; Can endure extreme drought and long salt life; General seed propagation; Cutting is difficult to take root. The national Populus euphratica forest covers an area of 400,000 hectares. The largest Populus euphratica forest in the world is concentrated in the Tarim River Basin in Xinjiang, China, with a natural forest area of 320,000 hectares, accounting for more than 90% of the national Populus euphratica forest area. The climatic conditions here are annual precipitation of 30 mm-60 mm, evaporation of 200 mm-3000 mm and extreme temperature of 42℃-30℃. Due to ecological deterioration and man-made destruction, the area of Populus euphratica forest is shrinking day by day (110.5 million hectares per year), and all of them will be cut down within 2 1 year at this rate. Subjective reasons for the sharp decline of Populus euphratica forest resources 1) Large-scale development and utilization of agriculture and animal husbandry In the early days of the founding of the People's Republic of China, people arbitrarily destroyed forests to open up wasteland; 2) Build a reservoir in the upper reaches of the river and intercept the water source at will, so that the Populus euphratica forest in the middle and lower reaches dies of water shortage. 3) Local residents cut down Populus euphratica forest as firewood fuel. Developing northwest to protect Populus euphratica forest. The International Poplar Committee has held many meetings, hoping that China can study Populus euphratica systematically and that the State Forestry Administration will study Populus euphratica in the Tenth Five-Year Plan. Project content: 1) Populus euphratica natural forest protection 2) Populus euphratica resources investigation 3) Populus euphratica excellent provenance, family investigation and superior tree selection 4) Populus euphratica salt-tolerant and drought-resistant mechanism 5) Populus euphratica clonal propagation 6) Populus euphratica hybrid breeding 5) Populus euphratica (Populus tomentosa) is distributed in Hubei. Someone put ciliates in this school. Four. Renewal of Poplar Varieties in 1950s and 1960s (First Generation) Populus euphratica-(Populus euramericana) Populus euramericana-Populus euramericana varieties. Poplar in Beijing-Populus davidiana (Populus americana)-Populus simonii-Populus simonii. Liaoning and other places) I-2 14 Populus americana/Europaea in 1960s and 1970s-Salang Populus-Populus americana-East Germany introduced 69 Populus-Populus deltoides clones-Populus deltoides clones-Italy introduced 63 Populus deltoides clones-Italy introduced 72 Populus deltoides clones-Italy introduced Half-sib family) Populus tomentosa-Populus tomentosa hybrid origin No.50-Populus americana selective clone-Populus americana selective clone-Populus americana n 30 16- Populus euramericana-Populus americana introduced in 1980s-1990s (fourth generation) 107-Holland. -Introduction and breeding-Italian poplar 1 10- Inter-factional hybridization-Populus deltoides-Populus deltoides dn 1 13- Populus euramericana-Populus canadensis-Populus deltoides-Populus deltoides.